Lamp base



FIG. 1 is a front elevational view of the lamp base, showing my new, original and ornamental design.

FIG. 2 is a rear elevational view thereof.

FIG. 3 is a side elevational view thereof, the opposite side being substantially similar thereto.

FIG. 4 is a top plan view thereof.

FIG. 5 is a bottom plan view thereof. 

The ornamental design for a lamp base, substantially as shown. 